Convio is massively sophisticated PaaS (Platform as a Service) and offers hundreds of features for organizations to administer their membership. Just about every big organization with a big membership uses Convio.
During my stint as Webmaster for the Electronic Frontier Foundation, we used Convio to email newsletters and "asks" (solicitations for donations), membership services (petition drives, mostly) and selling tickets to events, among other things. We used Convio but we didn't like it. The mere mention of "Convio" would produce scowls or cringes among those who had to use it, none bigger than on the face of the Executive Director who didn't like writing massive yearly checks to Convio.
My own experience with Convio was mostly confined to creating custom event web pages (example) on the Convio site using a mix of HTML, CSS, PHP and the Convio markup language. Sounds simple, right? It wasn't. The system for creating custom pages was labyrinthine at best. What I could easily do in an hour or two in Drupal would take me all day to do in Convio. The whole system was downright bizarre and unintuitive.
I came to think of Convio as similar to chemotherapy. It's got a time and a place, but it's difficult to endure and it makes your hair fall out.
Then I came across Nationbuilder, when my colleague Jim Ross wanted a new site with membership administration and he wanted it built on the Nationbuilder platform. Once I dove in, I could not believe how easy it was to use. Social media integration was flawless. Custom page templates were as easy as WordPress theming, easier even than Drupal theming. Adding members-only custom content is a breeze.
On Nationbuilder's site, they answer the question, How is NationBuilder different than Convio, Kintera and Blackbaud?
The answer blithely given:
If you've got money to burn and you've already learned how to use these tools, you might not want to switch. Otherwise, NationBuilder is an elegant replacement for these outdated donor management software suites. Our social CRM is designed to help you conduct donor outreach, interaction and contact logging from social media to phone and in-person contact, with rich analytics. You can print call sheets and download lists or your entire donor database easily.
This is ridiculously understated. After using Nationbuilder for a week, I could not understand why anyone would still use Convio. After another two projects (example), I can't believe people are not abandoning Convio like a burning warehouse and sprinting to Nationbuilder.